A trip to Yellowstone National Park took a terrifying turn for tourists after a family of black bears chased them across a bridge.
The group got a little too close for comfort for the mother black bear, who, along with her three cubs, sent the sightseers running when they surprised them.
The tourists were on a bridge in Yellowstone Park taking pictures of the bears below but the mama bear and her cubs took offence and suddenly appeared on the bridge.
The bear family started chasing the group of tourists as they all made their way back to their cars.
Footage shows visitors running away from the bears as Yellowstone park ranger John Kerr shouts "keep going! Go! Go!" off camera.
Black bears are usually shy of people but can quickly become very aggressive when they feel their young are threatened.